1. Field of the Invention
This invention relates to improvements in an airbag restraint system for protecting a passenger in a vehicle which has been in a serious collision or the like, and more particularly to an airbag which is provided therein with suspension belts to prevent the airbag from inflating generally in one direction upon being supplied with gas from a gas generator.
2. Description of the Prior Art
Hitherto, a variety of airbag restraint systems for automotive vehicles have been proposed and put into practical use in order to protect a vehicle passenger in the event of a serious vehicle collision or the like. Such airbag restraint systems are disclosed, for example, in Japanese Patent Publication No. 56-43890 and Japanese Utility Model Provisional Publication No. 61-185642.
The airbag restraint systems have usually been arranged as set forth below. The airbag restraint system includes an airbag which is momentarily inflated upon being filled with gas from a gas generator in the event of a serious vehicle collision or the like. The airbag has front and rear side sheet members which are formed of cloth material. The front and rear side sheet members are sewed at their peripheral portions to each other forming a bag-shape. The rear side sheet member is formed at its central part with a gas inlet through which the gas from the gas generator is supplied into the airbag.
Additionally, the airbag is provided therein with a plurality of suspension belts for the purpose of preventing the airbag from inflating to project generally in one direction or toward the vehicle passenger during inflation of the airbag upon being supplied with the gas. Each suspension belt is sewed at one end section to the inner surface of the front side sheet member. The other end section of the suspension belt is put between and sewed to a pair of belt catch members. The end sections of the belt catch members are in turn sewed to the rear side sheet member, at a location near the gas inlet, forming a circular sewed section in which the lines of the sewing threads extend in a generally circular pattern.
However, difficulties have been encountered in such a conventional airbag restraint system, as discussed hereinafter with reference to FIG. 9 of the drawings of the present application. When the airbag inflates under the pressure of the gas, a high tension is applied along the length of the suspension belts 2 the airbag through the end section 2a of the belts 2. At this time, the high tension unavoidably concentrates to a local point N at which the extension of the longitudinal axis of the suspension belt 2 crosses the circular sewed section 4 through which the belt catch members 6 are joined with the rear side sheet member 3. Therefore, there is a possibility that the sewing threads 5, at the point N, may break so that the belt catch members 6 are no longer joined to the rear side sheet member 3 of the airbag.